Installation heads for installing fasteners, such as for example studs are well known. An example of stud fastener installation heads can be found in U.S. Pat. No. 5,172,467. This patent is assigned to the assignee of the present invention which has a number of other patents directed to fastener installation heads for stud type fasteners and for female fasteners.
All known installation heads must overcome the problem of orienting the fastener within the head. If the fastener is not properly oriented, the fastener cannot be properly installed and in some instances the head can be damaged. The problem is particularly acute with stud type fasteners, and is even more of a problem with fastener heads that attempt to install the fastener, in the up direction or at an angle.
With reference to U.S. Pat. No. 5,172,467, a self-attaching installation apparatus is disclosed. This particular installation apparatus is particularly, although not exclusively, adapted for installation of stud-like fasteners. Stud-like fasteners have a projecting portion, such as a shank, extending from the body or head portion of the fastener. This type of fastener presents unique installation problems in mass production because the elongated fastener must be accurately oriented in the head and aligned with the die button to prevent damage to the installation apparatus.
Self-attaching stud fasteners are particularly adapted for transfer from a hopper or other source of fasteners to the installation head through for example, a flexible tube. The installation head receives the self-attaching fasteners, orients the fasteners for installation and drives the fastener against the panel and into a die member to form the fastener and panel assembly. In a typical application, the die button is located on the bottom shoe of a mechanical, hydraulic or pneumatic press, such as utilized by the automotive industry to form panels, brackets and the like. The installation head may be attached to the upper reciprocating die shoe, such that a fastener is attached to the panel with each stroke of the press. It will be understood, however, that the die press may include several installation apparatus assemblies, wherein several fasteners are installed with each stroke of the press.
The installation heads shown in FIGS. 15 and 20 of the '467 patent are fed fasteners which depend upon the fastener being installed in the down position or at most at a downwardly directed angle. The installation head receives fasteners from the tube coupling which is coupled to a hopper of stud fasteners. In the head illustrated in FIG. 15, the fasteners are blown by pneumatic pressure into the conical opening where it is automatically centered and oriented in the conical opening. As will be appreciated by those of ordinary skill in the art, the conical opening must be facing down to automatically orient the fastener. If the conical opening is facing up, the fastener will fall out of the opening or not align properly. In fact, with this installation head, unless the opening is at a generally right angle to the generally horizontal work surface into which the fastener is to be installed the fastener will not be properly aligned.
The conical recess in the nose member is composed of at least two spring biased members, each member having mating concave generally conical surfaces normally supporting the annular wall portion of the fastener and the plunger is adapted to drive the oriented fastener against the conical surface, spreading the spring biased members and installing the fastener in the panel. In the disclosed embodiment, the base member is attached to the moveable platen of a press and the base and nose members are interconnected by a piston. The piston is adapted to move the nose member, relative to the base member, to receive the fastener body portion free end in the plunger bore and the actuating means then operates the press to close the space between the base and nose members, driving the plunger through the plunger passage to install a fastener in the panel.
Another installation head is illustrated, see FIG. 20, which includes a housing having an elongated plunger reciprocal in a plunger passage, as described above, and a feed transfer means transferring fasteners to the plunger passage. The plunger includes a longitudinally extending bore configured to receive the elongated body portion or shank of the stud-like fastener. The end of the plunger is adapted to bear against the body portion of the fastener to drive the fastener into the panel, as described. The plunger is formed of at least two longitudinally extending mating parts intersecting the bore in the end of the plunger, including a first part having a concave portion of the bore facing the transfer means and a second relatively moveable plunger part adapted to close the bore and block the transfer path. The installation head includes actuation means adapted to longitudinally move the second plunger part, relative to the first plunger part, thereby opening the concave bore portion of the first plunger part. The transfer means then transfers a fastener to receive the fastener elongated body portion or shank in the plunger first part bore portion, orienting the fastener for installation. The actuation means then closes the second plunger part around the fastener elongated body portion or shank, ready for installation. Finally, the actuation means drives the plunger through the plunger passage and installs the oriented fastener in the panel.
In this embodiment, the transfer mechanism relies upon gravity to properly orient the fastener for transfers to the plunger. The transfer mechanism includes a shuttle piston which is actuated by a pneumatic piston. The piston moves the shuttle to the left moving a stud fastener from the position shown in FIG. 20 to the position shown in FIG. 23. The shuttle forces the shank of the fastener past the ball detentes (see FIG. 21) into engagement with rod magnets.
The stud fastener is dropped from the position 300a shown in FIG. 20, through the enlarged opening of the key hole slot 480 against the projecting plate 486. The die press is then actuated, lowering the upper platen, which closes the split plunger assembly as shown in FIG. 24. The upper plunger is thereby pressed into the cylindrical cartridge guide which presses against the upper annular portion of the second lower plunger member, closing the split plunger assembly and closing the axial bore in the end of the lower plunger as shown in FIG. 24. In the final installation, the upper die shoe platen engages the upper plunger, driving the self-piercing and riveting wall into a panel located on the die button, as shown in FIG. 25. The shuttle is now fully retracted and a stud fastener is dropped into the shuttle, as shown.
This embodiment wouldn't be able to transfer the fastener to the plunger if the installation head was oriented with the plunger pointing up. Although the plunger could install a fastener in the up direction, there is no disclosed method to properly feed the fastener to the plunger.
A still farther problem with both of the above installation heads is the increased size and complexity of these heads due to the need to properly feed and orient the fasteners. Again, the installation of stud type fasteners requires an accurately oriented fastener with respect to the plunger, panel into which the fastener is to be installed, and the die button. Both of these prior art heads require a fairly large and complex feeding system to insure the proper orientation of the fastener with respect to the plunger and the work surface.